1. Field of the Invention
The present invention relates to an optical associative identifier to be utilized in the field of optical data processing, and particularly relates to an improved optical associatively identifying apparatus.
2. Description of the Prior Art
There has been proposed a method of obtaining associatively a complete image from an incomplete image by an optical means, as shown in FIG. 1 (the prior art), referring to "Oyou Buturi (Applied Physics): Vol. 57, No. 10, pages 1,522 to 1,527. This method comprises forming multiple holograms 98 by changing the angle of incidence of the reference beam with regard to each of the complex conjugated reference images, forming a hologram 99 for the conjugated wave with regard to the hologram 98, putting an incomplete image A' on the hologram 98, and using the radiation of the beam from the hologram 98 along with the direction of the reference beam to record the complete image A, having high correlation with regard to the incomplete image A', so as to irradiate the hologram 99, thereby, resulting in an output of the complete image A. Further, this complete image is substituted in place of the input of the incomplete image to be fed back through a non-linear feed back amplifier 93, or a nonlinear processing step 94, thereby yielding only one associative output.
However, in this method, a recording media for writing high resolution images is necessary for a memory of recording holographic reference images. The currently available material satisfying such requirement is merely a photographically recording material. However, if the number of the reference images is large, one hologram cannot record all of the reference images. If all of the reference images are recorded in a plurality of separate holograms, the processing operation must use a mechanical changeover switch for holograms. Therefore, the method of the prior art requires the time-consuming development of a hologram, and further needs a very complicated operation for producing holograms because the reference beam has to be changed in its direction for each of the reference images. Further, it was impossible to process these holograms in real time. When the number of reference images is large, the search to find the image will take a great deal of time.
Further, in the prior art, because the range of spatial frequency for good refractive efficiency in producing holograms is fixed, it is impossible to select the range of spatial frequency efficient for the images for comparison or operation. It is therefore impossible to exert both of the outlined association or processing, and the comparison or processing of the detailed or fine portions of the image in the same memory.